This element allows you to define conditions which can be used to dynamically change the installer, e.g. the panels shown, the variables set, files parsed, files executed and much more. When you define a condition it will get a type and an id. The id has to be unique. Conditions can be referenced based on this id (e.g. with the RefCondition).

There are several built-in types of conditions. At the time of writing this, Izpack has the following built-in types:

There are also boolean types to combine more than one condition:

When you define a set of conditions, you just have to write as many <condition> tags as you like. A condition can take the following attributes:

The condition element can have several child elements depending on the type of this conditions. E.g. the VariableCondition has a name and value child element to specify, which variable should have a certain value to fullfil this condition.

This is an example which defines four conditions, two VariableConditions, a JavaCondition and a AndCondition which will refer to two of the first conditions.

<conditions>
   <condition type="variable" id="standardinstallation">
      <name>setup.type</name>
      <value>standard</value>
   </condition>
   <condition type="variable" id="expertinstallation">
      <name>setup.type</name>
      <value>expert</value>
   </condition>
   <condition type="java" id="installonwindows">
 <java>
   <class>com.izforge.izpack.util.OsVersion</class>
   <field>IS_WINDOWS</field>
 </java>
 <returnvalue type="boolean">true</returnvalue>
 </condition>
 <condition type="and" id="standardinstallation.onwindows">
   <condition type="ref" refid="standardinstallation"/>
   <condition type="ref" refid="installonwindows" />
 </condition>
</conditions>

Expression languages

Simple expression language

From IzPack 3.11 on, you don't have to define compound conditions because you can use a simple expression language. The language supports the following operators:

These simple expressions DO NOT follow the usual boolean logic with precedence rules. Instead, they are evaluated left to right in a simple way.

Thus, !conditionA+conditionB+!conditionC DOES NOT equal (!conditionA) && conditionB && (!conditionC), but equals !(conditionA && (conditionB && !(conditionC))).

So you should define complex conditions using the xml structure or use the Complex expression language.

Complex expression language

With IZPACK-577 and IZPACK-581 fixed and released, you can also use a more Complex expression language that evaluates using the boolean precedence rules, which is also reflected in the following table. The higher an operator is, the higher is its precedence.

!conditionA+conditionB+!conditionC equals (!conditionA) && conditionB && (!conditionC).

Parentheses may be added in the future.

More types of conditions can be defined by inheriting com.izforge.izpack.Condition class.

Built-in conditions

A number of built-in condition IDs are available for you.